1. Field of the Invention
The present invention relates to a wheel of synthetic material for bicycles or the like, for example for other single-track vehicles. The wheel has a rim, which is approximately U-shaped in cross section, for a tubed or tubeless tire; the wheel also has spokes which are unitarily molded onto the rim via injection molding which originates from the wheel hub.
2. Description of the Prior Art
In general, during manufacture of a wheel of synthetic material by injection molding in a mold, the wheel must, due to its geometrical shape, and in order to achieve optimum material properties, be centrally injection molded at the wheel hub, from where the synthetic material flows in the mold to the wheel rim. However, when a wheel comprising a rim, spokes, and hub is being homogeneously manufactured completely out of synthetic material, drawbacks result at the rim after the synthetic material has flowed through the spokes in the mold. These drawbacks result from the formation of a flow seam approximately in the middle of the rim portion between each two adjacent spokes. This formation of flow seams, especially with the use of synthetic material which is reinforced with glass fibers, leads to a considerable reduction of the ruggedness, the impact strength, and the appearance of the rim at these middle rim portions. Attempts were made to circumvent these disadvantageous flow seam formations in the rim profile of a spoked wheel of synthetic material by means of a multiple injection molding of the wheel at the rim. However, wheels produced pursuant to this method, have a great tendency toward distortion due to the varying pressure and shrinkage conditions in the mold. Furthermore, the formation of flow seams occurs in the vicinity of the hub of the wheel, as a result of which the problems of cold flow seams at the synthetic material hub, which receives the wheel bearings and is subjected to great stresses, lead to a particularly critical reduction in strength.
An object of the present invention is to avoid the drawbacks of heretofore known wheels of synthetic material, while still providing for injection molding which originates at the wheel hub.